FYI, the software in question is now at v 9.1.1 - not yet reflected on MU.
A (rather long) foreword:
I've been using Aperture until its dying day, resisting Adobe "bloatware" and licensing policy like a lone samurai left on the battlefield surrounded by enemies:) I then bit the bullet (the sword?) and bought LR6, and was surprisingly pleased with it - it required minimal workflow adjustments, the metadata and catalogs management is way better than Apple's offering, and it's quite quick and more or less trouble-free. I would like to stress that I do not earn my living by photography and therefore have less stringent demands than most professionals. However, RAW conversion in LR6, although better than in Aperture, is still not enough for me. Hence DxO Optics Pro 10, which I use to treat RAW files from inside LR6 and then reimport them back for further manipulation. This has been my setup for the last 16 months, and I was quite pleased with it. Then, out of sheer curiosity, I tried CaptureOne.
C1 has one huge advantage - its RAW processing engine easily beats anything out there. No questions. Full stop. Its colour correction is the easiest to use and the most natural looking, unless you want to go mad with it - but even then you'll be pleased with the results. Noise reduction is perfectly adequate - in most complicated cases DxO "Prime" technology is better, but you can still tell NR has been applied, and let's be honest, with modern cameras' low light performance you'd rarely need to apply massive amounts of noise reduction. The camera/lens database is where DxO outshines everything else on the market, but nearly all the decent lenses and bodies are catered for by C1. Sharpening is excellent if you've got decent raw material (read "decent lens and steady hands") and just about passable if you haven't, but then it's your fault:)
C1 has one huge disadvantage - it does not happily integrate with other software. And it's not a good news, because its cataloging system is not in the same league as LR6, although not as appalling as in previous versions. Confusing Catalogs and Sessions (although I see the pro's logic behind that), switching between catalogs takes forever and in rare instances can hang the programme. Cataloging options are many, but not as extensive as LR6 or PhotoMechanic. IPTC is supported, but again, not to Adobe's standard. On a sweeter note, you do get hierarchical (nested) keywords - finally!
Then there's plugin support, of which there's none. I use Nik and Macphun by a bucketload, and having standalone versions is a godsend - C1's "Edit in..." command sends your file for processing to an external editor and then re-imports the result. Kinda like a plugin. But try to send two or more files to a HDR editor - and it returns... yep, two or more different files, none of which is HDR, and the actual HDR programme may or may not quit unexpectedly.
So you can integrate some other apps into your C1 workflow, but you can't easily integrate C1 into anything else, in my case LR6. There are workarounds and roundtrips from LR6 to C1, but to me they seem a bit too clumsy, and by doing so you separate your original RAW files from the resulting DNG files, which means more external HDs by the day. You can import your LR6 catalogs into C1 and even retain a few basic adjustments you've made in LR6, but not many. You can also import your keywords from any text file, and - die, Adobe! - you can assign your own keyboard shortcuts all you like!
So here's my dilemma: image quality or convenience in cataloging and post-processing? I've setup a separate HD for use with CaptureOne trial (no restrictions, good for one month) and over the next few weeks will try to get used to C1's catalogs and other quirks, and if anyone's interested I'll report back once there's more to report.
At the moment CaptureOne gets 4.5 stars from me purely on my impression of its RAW conversion and its possibilities. I can replicate the results in DxO fairly closely, but not quite, especially on less straightforward shots. The excitement can wear thin though, especially if my struggle with catalogs ends in disaster...